Another interesting work was bringing some shape back to this nice wild olive. I've had
this tree for 8 years now but since I can't provide the best protection
during winter for it it has never grown very well. So this was only the
second wiring during all those years. Still, slowly but surely it will
grow up to be a nice bonsai one day.

Eventually after inspecting the base of the trunk I noticed something I was afraid of, but knew would happen some day. A good part of the deadwood at the base was very soft, wet and rotten.
It is tipical for dead wood to rot faster when in contact with soil because it is in contact with water the better part of time. And since this tree is fairley young, which means that its wood is not very hard, wood rotting accures even faster. Therefor this was no surprise to find such a sight after 9 years of having this tree.

So what to do next? If I had left this untouched the rotting would continue until it would eat away the whole dead trunk at the base. You can't really prevent rotting of deadwood at soil level, but there are a few ways to noticably slow it down. First you have to remove all or at least most of the soft rotten wood, until you get to the wood that is still hard.

Then you wait a little for it to dry out and then burn it with a torch. Fire is known to make wood harder. But you have to be carefull not to fire it too much which will just turn the wood into coal and you will end up with even less of the trunk.

Next step is to apply lime sulphur. This is the most commen technicque to preserve deadwood on a bonsai, so why bother trying to figure anything new out. But since this part will be more exposed to water apply more layers of the lime sulphur.